docs: def validate_field(self, field_name: str) -> bool:
          """
          Complain if a field in not in the schema
          Args:
              field_name:
  
          Returns: True if the field is present.
  
          """
          if field_name in {"@id", "@type"}:
              return True
          result = self.schema.has_field(field_name)
          if not result:
              # todo: how to comply with our error handling policies?
              raise UndefinedFieldError("'{}' should be present in the knowledge graph schema.".format(field_name))
          return result